<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>

        var age = prompt('请输入您的年龄');
        // 引引++
        // '+ age +'
        var result = '您今年' + age + '岁啦';

        alert(result);

    </script>
</body>
</html>